如何使用可选的秒参数创建DateTimeformatter [英] How to create DateTimeformatter with optional seconds arguments

问题描述

我正在尝试创建一个 DateTimeformatter 来验证以下日期时间：

I am trying to create a DateTimeformatter to validate following date times:

String date1 = "2017-07-06T17:25:28";
String date2 = "2017-07-06T17:25:28.1";
String date3 = "2017-07-06T17:25:28.12";
String date4 = "2017-07-06T17:25:28.123";
String date5 = "2017-07-06T17:25:28.1234";
String date6 = "2017-07-06T17:25:28.12345";
String date7 = "2017-07-06T17:25:28.123456";
String date8 = "2017-07-06T17:25:28.";

我已尝试使用以下日期时间格式器来验证上述日期：

I have tried the following date time formatter to validate above dates:

public static final String DATE_TIME_FORMAT_PATTERN = "yyyy-MM-dd'T'HH:mm:ss";
DateTimeFormatter formatter1 = new DateTimeFormatterBuilder()
                                   .appendPattern(DATE_TIME_FORMAT_PATTERN)
                                   .appendFraction(ChronoField.MICRO_OF_SECOND, 0, 6, true)
                                   .toFormatter();

它适用于所有上述日期，但根据我的要求，它应该以<$ c失败$ c> java.time.format.DateTimeParseException for date8 。

It works fine for all the above dates, but according to my requirement it should fail with java.time.format.DateTimeParseException for date8.

注意：我知道我可以通过以下格式化程序实现预期的结果：

Note: I am aware that I can achieve expected result with following formatter:

DateTimeFormatter formatter2 = DateTimeFormatter
                       .ofPattern("yyyy-MM-dd'T'HH:mm:ss[.SSSSSS][.SSSSS][.SSSS][.SSS][.SS][.S]");

但我想知道我们可以通过更改 formatter1来达到预期的结果？

But I wanted to know that can we achieve expected result by changing in formatter1?

用于解析我使用的日期：

For parsing the date I am using following:

LocalDateTime.parse(date1, formatter1);

推荐答案

您必须创建一个可选部分（使用 optionalStart（）和 optionalEnd（）方法）包含小数点后跟1到6位数字：

You must create an optional section (using optionalStart() and optionalEnd() methods) containing the decimal point followed by 1 to 6 digits:

String DATE_TIME_FORMAT_PATTERN = "yyyy-MM-dd'T'HH:mm:ss";
DateTimeFormatter formatter1 = new DateTimeFormatterBuilder()
    .appendPattern(DATE_TIME_FORMAT_PATTERN)
    // optional decimal point followed by 1 to 6 digits
    .optionalStart()
    .appendPattern(".")
    .appendFraction(ChronoField.MICRO_OF_SECOND, 1, 6, false)
    .optionalEnd()
    .toFormatter();

这从 date1 解析为 date7 并使用 date8 抛出 java.time.format.DateTimeParseException 。

This parses from date1 to date7 and throws a java.time.format.DateTimeParseException with date8.

这也有同样的作用：

String DATE_TIME_FORMAT_PATTERN = "yyyy-MM-dd'T'HH:mm:ss";
DateTimeFormatter formatter1 = new DateTimeFormatterBuilder()
    .appendPattern(DATE_TIME_FORMAT_PATTERN)
    // optional decimal point followed by 1 to 6 digits
    .optionalStart()
    .appendFraction(ChronoField.MICRO_OF_SECOND, 1, 6, true)
    .optionalEnd()
    .toFormatter();

这篇关于如何使用可选的秒参数创建DateTimeformatter的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！